1. University of Pitesti,Faculty of Electronics, Comm. and Computers,Pitesti,Romania
2. Group of Research in Electrical Engineering of Nancy (GREEN), University of Lorraine-GREEN,Nancy,France
3. King Mongkut's Univ. of Technology North Bangkok,Renewable Energy Research Centre (RERC), Faculty of Technical Education,Bangkok,Thailand
4. ICSI Energy, National Research and Development Institute for Cryogenic and Isotopic Technologies,Ramnicu Valcea,Romania,240050